feat(tests): add 16 advanced distractor-rich scenarios

The 2026-08-30 suite-health review found 223/283 tests saturated. These
16 target the failure modes that still discriminated, one per existing
subcategory across all eight categories:

- multi-constraint reasoning: infeasible-plan detection, conflicting
  delegation policy, adversarial tool descriptions
- forensic root-causing from noisy evidence: RAG stage attribution,
  EXPLAIN ANALYZE with a red herring, interleaved multi-source incident
  logs, README-vs-config conflict resolution
- composed gotchas: a Go 1.22 capture + named-return-defer trace, a
  Python late-binding + shared-mutable-default trace
- constraint math: context-budget packing, capacity-fill projection,
  MVCC anomaly classification, Docker layer-rebuild prediction, dual-key
  rotation overlap, freeze-window scheduling, an open-redirect exploit
  chain

Every answer is a structured JSON value scored by an exact evaluator,
never a prose heuristic (the source of every false positive in the
review). A ground-truth self-consistency test asserts each documented
correct answer scores 1.0 through its real evaluator.

internal/tests/catalog.go

@@ -26,5 +26,6 @@ func All() *testkit.Registry {
 	registerHardTests(r)
 	registerScenarioTests(r)
 	registerSaturationTests(r)
+	registerAdvancedTests(r)
 	return r
 }